Submitted to: Part of Title 22 of Arkansas State Law
Publication Type: Other
Publication Acceptance Date: November 1, 2005
Publication Date: November 21, 2005
Citation: Moore Jr, P.A. 2005. Sewage sludge protective rate. Part of Title 22 of Arkansas State Law. p. 3.

Interpretive Summary: Recently in Arkansas a series of laws have been passed under Title 22 which regulate the application of poultry litter and other fertilizers within parts of the state designated as nutrient surplus areas. The rate of application to be allowed in these areas will be determined by either a nutrient management plan approved by the Arkansas Soil & Water Conservation Commission or at a "protective rate". The "protective rate" is defined as the agronomic rate or other rate as determined by the commission of a designated nutrient that provides for proper crop utilization and prevention of significant impact to waters within the state. Previously, our group had determined the Protective Rate of poultry litter for Arkansas using the Arkansas Phosphorus Index. Hence, this same approach was utilized to determine the Protective Rate of sewage sludge for various levels of soil test phosphorus. Basically this rate limits the amount of sewage sludge that can be applied based on the water soluble phosphorus content of the sludge and the soil test phosphorus of the receiving field. The upper cutoff for soil test phosphorus above which no sludge could be applied was 1400 pounds per acre. In addition to these rates, which are based on phosphorus, sewage sludge shall be applied at rates less than or equal to: (a) rates allowed by federal law regulating heavy metal and pathogen applications in sewage sludge, and (b) the agronomic rate based on nitrogen needs of the crop as outlined in Arkansas state law. Municipalities may use chemical amendments containing aluminum or iron to reduce soluble phosphorus in sludge. However, calcium amendments added strictly for this purpose will not be allowed, since calcium phosphate minerals are not stable under slightly acidic conditions, such as that found in Arkansas soils.

Technical Abstract:
The 84th General Assembly of Arkansas recently passed the Arkansas Soil Nutrient Application and Poultry Litter Utilization Act which states "It shall be a violation of this subchapter to apply designated nutrients to soils or associated crops within a nutrient surplus area unless the nutrient application is done in compliance with a nutrient management plan approved by the Arkansas Soil and Water Conservation Commission or at a protective rate established by the commission". The "protective rate" is defined as the agronomic rate or other rate as determined by the commission of a designated nutrient that provides for proper crop utilization and prevention of significant impact to waters within the state. Previous work completed by our group determined the Protective Rate of poultry litter for Arkansas using the Arkansas Phosphorus Index under severe conditions (high runoff class, 1-2 tons erosion/acre, surface applied in spring, hayed & grazed). Hence, this same approach was utilized to determine the Protective Rate of sewage sludge for various levels of soil test phosphorus. In addition to these rates, which are based on phosphorus, sewage sludge shall be applied at rates less than or equal to: (a) rates allowed by federal law regulating heavy metal and pathogen applications in sewage sludge, and (b) the agronomic rate based on nitrogen needs of the crop as outlined in Arkansas state law.
Municipalities may use chemical amendments containing aluminum or iron to reduce soluble P in sludge. However, calcium amendments added strictly for this purpose will not be allowed, since calcium phosphate minerals are not stable under slightly acidic conditions, such as that found in Arkansas soils.